as the probe is inside a metal sleeve, there does seem to be some inertia in the measurement now

"Dead-time" in PID jargon.

I knew that :coughs: !!

Quote

Quote

I may well add PID processing - which should stop the overshoot

Not necessarily. There is a conflict between getting the response you want, the dead-time, and overshoot. If possible, you should first strive to reduce the dead-time as much as possible. That will make working with PID much much easier.

indeedI'm looking at removing the end of the metal sleevethat way the thermocouple will be nicely inside the ovenbut still in free air (aka dangling!)

there are only 10 types of peoplethem that understands binaryand them that doesn't

stripped it down againthe plan was to "simply" saw 1/3" or so off the sealed end, so the thermocouple would hang in the middle of the oventook a hacksaw to it - no effectlooks like it's stainless steel

tried a Dremel with one of the little "parting" discsknife through butter!

cleaned the end with the same discso now have a slightly shorter tubewith thermostat out in the open

tried a profile run last nightMUCH closer to the first graph (several posts ago)close enough that the dead time seems to have gone away

I thought your other curve followed your desired profile better.Am guessing its not all that critical if it can be controlled by hand just rotating a temperature control knob and a thermocouple stuck it the tines of a fork to hold in place near the card being reflowed ...

further update on the probe that I had to fixbefore leaving eBay feedback I emailed the vendorvery responsive - bottom line got £1.00 refundI'm happy - the probe works and it (now) only cost me £1.52the fix was dead easyhere's a picture of the problem/fix

the red circle shows the stainless steel outer after I cut it backthe blue circle is where the outer stopped originallywith the frayed wires shorting out the probe

here's the final circuit(went through several iterations to get there - as you do!)and here's the triac heater control

In your circuit, what's the purpose of R5? Also, I see you have the mains hot connected to MT2 on the triac. Does it matter which way the triac is wired? Would it make a difference if MT1 went to mains hot and MT2 went to the oven?